This invention relates to the field of wireless data communication. More specifically, this invention describes a novel and improved method and apparatus for scheduling packet data transmissions in a wireless data communication system.
In a wireless communication system, each of a plurality of base stations communicates with a set of mobile users. Such wireless communications could take the form of low-delay circuit-switched voice or video transmissions. Alternately, the communications could take the form of high bit rate packetized data transmissions. Examples of such high bit rate packet data systems include the TIA/EIA/IS-856 standard (cdma2000 High Rate Packet Data Air Interface Specification, Telecommunications Industry Association, Arlington, Va., November 2000) and the TIA/EIA/IS-2000.2 standard (Physical Layer Standard for cdma2000 Spread Spectrum Systems—Release C, Telecommunications Industry Association, Arlington, Va., May 2002).
In general, packet data transmissions are much more delay tolerant than real-time voice or video transmissions. Therefore, scheduling can be used at the base station in order to take advantage of the changing wireless channel conditions for each of the users requesting service from the base station. After performing scheduling, the base station can transmit packets to as few as one user at any given time. In general, the scheduling algorithm must attempt to meet two conflicting goals. First, the operator of the wireless system would wish to maximize the amount of data sent through the system in order to take full advantage of the system resources and thereby increase the revenue that the system would generate. However, maximizing the overall system throughput may result in a highly unequal distribution of service to the pool of mobile users. A small group of users could receive an excessive allocation of time or packets to the detriment of the service to the remaining users. Therefore, the scheduling algorithm must also provide a fair allocation of resources to all the mobile users.